ALSA Audio Playback

Send audio to sound card for playback using ALSA

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Add-On Required: This feature requires the Embedded Coder Support Package for BeagleBone Black Hardware add-on.

  • ALSA Audio Playback block

Libraries:
Embedded Coder Support Package for BeagleBone Black Hardware

Description

The ALSA Audio Playback block sends audio data to the audio output devices, such as speakers or headphones, connected to the hardware. The block uses an Advanced Linux Sound Architecture (ALSA) driver framework to send audio data.

The block accepts an N-by-C matrix, where N is the samples per channel, and C is the number of channels supported by the audio. The block determines these values from the input signal.

Note

To use the ALSA Audio Playback block with audio devices that support more than two channels, you must have an Audio Toolbox™ license.

Algorithm

Consider a Simulink® model that includes a ALSA Audio Capture block and a ALSA Audio Playback block. The ALSA Audio Capture reads stereo audio data from the microphone connected to the audio input connector of the hardware. The block outputs data as a 3-by-2 matrix. At each sample time, the ALSA Audio Playback block accepts the audio matrix and sends audio to the headphones connected to the audio output jack of the hardware.

The ALSA Audio Playback block determines the sample time (Ts) from the samples per audio channel (N) and sampling frequency (Fs).

Ts = N / Fs

For example, if N is 4410 samples and Fs is 44,100 Hz, the block sample time is 4410/44,100 = 0.1 seconds.

N is the number of samples per audio channel. The block determines the value of N from the input data. Fs is the sampling frequency of the input data specified in the Audio sampling frequency (Hz) parameter.

Ports

Input

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The block accepts an N-by-C matrix, where N is the samples per channel, and C is the number of channels supported by the audio. The block determines these values from the input signal.

Data Types: int8 | int16 | int32

Parameters

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Specify the ALSA audio input device connected to the hardware from which the block reads audio data.

This value comes from the ALSA configuration file, /usr/share/alsa/alsa.conf, located on the BeagleBone® Black hardware.

Specify the sample rate used by the audio input device to read audio data, in Hz. The sample rates listed in the Audio sampling frequency (Hz) parameter depends on the audio input device.

Enter the amount of audio buffered by the block. A higher value results in smoother audio at the expense of increased latency.

Version History

Introduced in R2014b

See Also

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